This may have been covered in another thread(I'm new at this) but what about the primary countershaft gearbox getting full of dust and debris due to the pressure blowing the dipstick out. It seems like there would be a vent but I can't find one.
PRIMARY COUNTERSHAFT GEARBOX DIPSTICK BREATHER ALLOWS DUST AND DIRT TO ENTER THE GEARBOX
AH168685 primary countershaft gearbox STS combines dipstick breather allows contaminates to enter the gearbox
These improved dipsticks are constructed with a foam filter rather than twisted chain and are painted black
AH173466 Dipstick ( primary countershaft gearbox, 9650STS and 9750STS Combines only